Background Disease activity has been shown to be a good predictor of joint damage in patients with rheumatoid arthritis (RA). Different measures including composite indices and individual instruments are available to monitor disease activity. Their relation to radiographic progression is important to be informed on predictive validity.
Objectives To investigate the relationship between the different disease activity indices (DAI) and their individual components and radiographic progression in patients with RA.
Methods A systematic literature review until July 2013 was performed by two independent reviewers using Medline and EMBASE databases. The research question was formulated according to the PICOS method: Population (RA patients); Intervention (DAI including DAS, DAS28, SDAI, CDAI, RADAI and RAPID and individual instruments or scales including patient's global health, patient's global disease activity, pain, evaluator's global disease activity (EGA), all on a VAS, CRP, ESR, and swollen and tender joint count (SJC, TJC)); Outcome (radiographic progression); and Setting (Longitudinal studies with at least 12 months of follow up).
Using a systematic extraction data form developed for this specific purpose, both reviewers independently extracted data for each study and evaluated the quality and potential biases of them (range 0-6 points) according to the Hayden tool. Results were weighted according to a statistical hierarchy based on the type of disease activity measure employed in the analysis as independent variable (cumulative assessment over the whole study period were considered more appropriate than just baseline measures) and the type of analysis (multivariable was considered more appropriate than univariable).
Results Fifty five studies from 1232 citations were included. Most of the studies were prospective cohorts and had an overall quality score ≥4 points. Radiographic progression was mainly assessed using the modified Sharp van der Heijde or Larsen scoring methods and the period to evaluate progression ranged between 12 and 240 months. Among those studies using cumulative assessment and multivariable analysis, six studies assessed the relationship between at least one DAI (three for DAS28, two for DAS and one including DAS, DAS28, CDAI and SDAI) and radiographic progression and they all reached statistical significance. Further, seven studies investigated the relationship with single instruments: three of them reported data for TJC, six for SJC, one for EGA, one for pain, four for ESR and four studies for CRP. In these studies, only SJC and ESR were related to radiographic progression while no association was found for TJC. Data with respect to CRP is conflicting. Reported literature for patient's global health, pain and EGA is limited and does not support an association with progression of joint damage.
Conclusions Published data indicates that composite disease activity scores are more related to radiographic progression than their individual components. Therefore, these are the optimal tools to monitor disease activity in patients with RA. The best performing single instruments are SJC and ESR.
Acknowledgements VNC was sponsored by an unrestricted educational grant from Roche and the Fundaciόn Española de Reumatología.
Disclosure of Interest None declared
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